Which method utilizes urease and glutamate dehydrogenase for the quantification of serum urea?

Which method utilizes urease and glutamate dehydrogenase for the quantification of serum urea?

• A. Berthelot
• B. Coupled enzymatic
• C. Conductimetric
• D. Indicator dye

Answer: (B)

Two enzymes are used in sequence to convert the amount of urea into a measurable signal. First, urease hydrolyzes urea to ammonium. Then glutamate dehydrogenase uses that ammonium with α-ketoglutarate and NADH to form glutamate and NAD+. The reaction consumes NADH, and the rate of NADH decrease (usually read at 340 nm) is proportional to the urea concentration. This setup is a coupled enzymatic method because it links two enzymatic steps to produce the signal. Other approaches don’t use this two-step enzyme cascade: Berthelot-type methods are colorimetric reactions for ammonia, not a GDH-coupled process; conductimetric methods monitor changes in conductivity; indicator dye methods rely on dye color changes without the GDH coupling.

Two enzymes are used in sequence to convert the amount of urea into a measurable signal. First, urease hydrolyzes urea to ammonium. Then glutamate dehydrogenase uses that ammonium with α-ketoglutarate and NADH to form glutamate and NAD+. The reaction consumes NADH, and the rate of NADH decrease (usually read at 340 nm) is proportional to the urea concentration. This setup is a coupled enzymatic method because it links two enzymatic steps to produce the signal.

Other approaches don’t use this two-step enzyme cascade: Berthelot-type methods are colorimetric reactions for ammonia, not a GDH-coupled process; conductimetric methods monitor changes in conductivity; indicator dye methods rely on dye color changes without the GDH coupling.